The present invention is based on Japanese Patent Application No. 11-6311, the content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a toner for developing an electrostatic latent image for use in electrostatic printing, electronic photographs and the like.
2. Description of the Related Art
The demand for a high degree of fluidity in toners for colorization and digitalization of printers and copiers in recent years typically has been achieved by adding to the toner inorganic fine particles such as silica fine particles and titania fine particles and the like as a fluidizing agent. However, when a large amount of such fluidizing agent is added to achieve a high degree of fluidity, disadvantages often arise inasmuch as the fluidizing agent may pass through the cleaner unit provided with a blade cleaning mechanism so as to remain on the photosensitive member and cause filming and black spots (BS) on the image which are called image defects.
A toner has been proposed for preventing filming and black spots as well as participating in polishing by the cleaner unit, by adding to inorganic particles having a number-average particle size of approximately 80xcx9c800 nm to the toner, particularly strontium titanate particles to counter the aforesaid disadvantages. However, it is well known that inorganic particles are treated by hydrophobic processing via surface processing by a silane coupling agent so that the fluid characteristics and electrostatic properties will not change even under variable humidity and temperature environments.
When strontium titanate particles having a number-average particle size of approximately 80 to 800 nm are subjected to such hydrophobic processing, the surface treating agent does not adequately treat the strontium titanate particles, and since the hydrophobicity is not improved, there is only minor improvement in toner charge level adjustability or charge environmental stability despite the addition of the hydrophobic strontium titanate.
An object of the present invention is to provide a toner having excellent charge environmental stability.
Another object of the present invention is to provide a toner having excellent charge level adjustability.
Yet another object of the present invention is to provide a toner having excellent polishing characteristics.
The present invention relates to a toner comprising toner particles and an external additive comprising strontium titanate particles that have a number-average particle size of 80 to 800 nm and do not have a peak of strontium carbonate in qualitative analysis by X-ray diffraction.